Will millimeter waves become the “killer” to break through the shackles of 5G development?

ON June 6, 2019, the Ministry of Industry and Information Technology issued the “Basic Telecom Business Operation License” to four operators, China Telecom, China Mobile, China Unicom, and China Radio and Television. With the opening of the first year of 5G commercial use in China, large-scale 5G network construction has been fully launched. For all walks of life, industrial applications based on features such as large broadband, massive connections, low latency, and high reliability are poised for development. At that time, as the strong backing of the beautiful visions such as the Internet of Things and artificial intelligence, the upstream and downstream of the industry chain were full of infinite imagination for the future development of 5G.
Now, two years have passed since the issuance of 5G licenses. According to data released by the Ministry of Industry and Information Technology in June, nearly 850,000 5G base stations have been built in my country, forming the world’s largest 5G independent networking network, and there have been more than 10,000 5G industry application innovation cases. With the blessing of 5G, application scenarios represented by 4K/8K ultra-high-definition video, VR/AR, autonomous driving, drones, and intelligent robots are developing rapidly.
However, at a time when the construction of 5G network infrastructure is in full swing and terminal applications are breaking out one after another, limited spectrum resources have virtually formed a “shackle” that restricts the development of 5G.

  “Optimizing stock” and “reclaiming new land” in parallel
As a natural resource that exists in nature, the radio spectrum cannot be seen or touched, but can be used as a transmission carrier to send and receive information such as symbols, words, sounds, and images. As a fixed resource, radio frequency spectrum has become especially precious in the intelligent era when the scale of end users is increasing day by day. In recent decades, the radio frequency spectrum has become more and more crowded. How to ensure the iteration of communication technology and the innovation and development of industrial applications, Effective, reasonable and full use of spectrum resources has become a difficult problem that must be faced in the field of communications.

There are three main reasons for the shortage of radio spectrum resources in the 5G era:
The first is the slow intergenerational upgrade of mobile communications, which exacerbates the contradiction between spectrum supply and demand. At present, 2G and 3G are accelerating their withdrawal from the network, but in fact, 5G has been commercialized for two years. 3G still occupies some high-quality spectrum resources, and it will be difficult to vacate spectrum resources if the network cannot be completely withdrawn.
The second is the limitation of radio spectrum policy, which intensifies the contradiction between supply and demand of spectrum. Taking the U.S. spectrum policy as an example, the 5G networks currently deployed by U.S. operators mainly focus on high-frequency millimeter waves, because according to the policy, high-quality intermediate frequency bands have been granted to the military for use, which is difficult to vacate, resulting in a shortage of spectrum resources.
Finally, the high cost of spectrum acquisition aggravates the contradiction between spectrum supply and demand. This is even more evident for overseas operators, whose spending on auctioning 3G, 4G, and 5G spectrum has brought enormous pressure on their network construction. Although domestic spectrum is awarded to operators, the game between operators will also consume a lot of costs.
If the wireless network is like a paddy field, the wireless spectrum is the land on which the rice is grown. As the population increases and food demand increases, if everyone wants to “eat enough”, it is necessary to increase production. In the face of limited land, there are only two ways to achieve high yields – optimizing stock and reclaiming new land.
The optimized inventory is mainly reflected in the two levels of 2G and 3G accelerated network withdrawal and operator spectrum sharing.

First of all, the withdrawal of 2G and 3G networks is a foregone conclusion. In the past few years, global operators have successively promoted frequency reduction and withdrawal of 2G and 3G networks, freeing up spectrum resources for 4G and IoT use, or re-cultivating some 4G frequency bands. In 5G, certain results have been achieved. For example, China Mobile currently owns 5G resources in the 2.6GHz frequency band, of which the 2575-2635MHz frequency band is re-cultivating the existing 4G frequency band of China Mobile.
Second, the spectrum sharing mode is being explored in the deep water area. At present, there are mainly two ways. One is spectrum sharing between different networks within an operator. The current technological development can fully realize spectrum sharing between different intergenerational networks; the other is Spectrum sharing between different operators, “co-construction and sharing” has gradually become an innovative model for the current 5G development. For example, China Telecom and China Unicom each hold 100MHz intermediate frequency spectrum, and both parties can use 200MHz spectrum resources after sharing.
Reclaiming new land points to the undeveloped and resource-rich frequency bands, and millimeter wave stands out.

  Why mmWave?
First of all, the simplest reason is that the millimeter wave frequency band is rich in resources. Millimeter waves generally refer to the radio spectrum with frequencies in the range of 30GHz to 300GHz, while the actual frequency band used by 5G is between 24GHz and 100GHz. The superiority of wave spectrum resources is beyond doubt.
Second, millimeter waves can support ultra-low latency. 5G adopts OFDM technology, which divides the carrier bandwidth into sub-carriers one by one. At the same time, it is also divided into time slots one by one in time, and the two dimensions of sub-carriers and time slots are used to transmit data together. The subcarrier width is inversely proportional to the time slot length. The subcarrier spacing used by millimeter wave is much wider than that of Sub-6G, generally 120KHz, so the length of each time slot can be very short. 5G schedules data in units of time slots. The shorter the time slot length, the smaller the 5G delay at the physical layer.
In addition, millimeter waves can support high-precision positioning. Millimeter waves are supported by beamforming, with narrow beams, good directionality, and extremely high spatial resolution. At the same time, due to the small delay, ultra-high-precision positioning can be achieved.
Undoubtedly, based on the current situation of domestic spectrum resources and the promotion of relevant favorable policies, millimeter waves in the ultra-high frequency band are the most valuable and potential spectrum resources in the 5G era. cultivated pure land.
As early as March 2020, the “Notice on Promoting the Accelerated Development of 5G” issued by the Ministry of Industry and Information Technology proposed to release some 5G millimeter-wave frequency band frequency usage plans in a timely manner, and organize millimeter-wave equipment and performance tests in combination with the national frequency planning schedule. Prepare for the commercial use of 5G millimeter wave technology. Subsequently, on April 30, 2021, the website of the Ministry of Industry and Information Technology issued a “public solicitation for opinions on the “5G Application” Sail “Action Plan (2021-2023)”, which clearly proposed to strengthen the guarantee of 5G frequency resources. One of the highlights is to explore The new frequency supply system, on the one hand, is the exploration of the 5G millimeter wave frequency system, and on the other hand, the exploration of the 5G supply Internet dedicated frequency.
However, the merits and demerits are mixed. Although millimeter wave is a precious resource in the 5G era, it also has its own shortcomings, resulting in its development speed is not as good as expected. Among them, poor coverage is the Achilles heel of millimeter waves – due to the high frequency and short wavelength of millimeter waves, the free space propagation loss, penetration loss and diffraction loss are large, and the diffraction ability is poor, resulting in a small coverage of a single cell. The actual measurement shows that even if the terminal is in a line-of-sight (LoS) environment, the coverage of a millimeter-wave cell is only about 100 meters, which is almost the same as the Wi-Fi coverage.
In addition, the unit price, construction and operating costs of millimeter-wave base stations are much higher than those of Sub-6GHz, and in the face of the dilemma that millimeter-wave needs to build more base stations, the high cost will undoubtedly further increase the threshold for its industrial landing.
Despite this, the advantages of millimeter wave in the 5G era still attract great attention from the industry chain, and the call for its early commercial use has been louder than ever.
In this context, Qualcomm, as an industry leader, also pays attention to the huge development space of 5G millimeter wave, and will hold the 2021 Qualcomm 5G & AIoT Technology Open Day event in Xi’an on July 15, specially invited Qualcomm technical experts and partners Share and discuss with industry star enterprise experts on hot topics such as 5G application trends, 5G and millimeter wave technology progress and development trends, 5G communication modules and terminal development trends, and excellent industry cases.